LighttheCandle,
I had the same problem at your age. I imagine attending Toastmasters would make a lot of sense.
Otherwise it just takes time. Until you gain a bit more self-confidence and your self preservation instincts kick in all the "tricks" in the world aren't going to change how your voice projects. In my case, I got tired of my soft voice and seeming innocence actually bringing people who I didn't want closer to me closer so that they could hear my responses.
Best of luck, you'll get there.
